IACT303 – INTI 2005 IACT303 – INTI 2005 World Wide NetworkingWorld Wide NetworkingIACT303 – INTI 2005 IACT303 – INTI 2005

World Wide NetworkingWorld Wide Networking

Organisation of the InternetOrganisation of the InternetThe University of WollongongThe University of Wollongong

Objectives• This lecture we look at:

– Understanding the Domain Name Service

Domain Name System (DNS)

• There are hundreds of countries, millions of networks and millions of hosts.

• How do we keep track of all the nodes and networks.

• Well we use a service called DNS (Domain Name Service).

• The Domain Name Service is a distributed database which provides a lookup table for hostnames and IP addresses.

• We as human refer to nodes on the internet through names. In order for this to work we need to convert these high level names into addresses.

• DNS does this, its called name resolution.

• The Domain name system also gives us a network hierarchy. It is responsible for giving structure to the Internet (from the users perspective).

The History Behind the Domain Name Service

(DNS)• When the Internet was first born (ARPANET)-

the mapping between Hostnames and IP addresses was done in small files.

• If a site wished to add a new computer to the network, they choose a name and added it to such files.

• These files were distributed to other sites. Such a process consumed considerable bandwidth.

• That said there were consistent problems keeping the data between sites up to date and in sync.

• It soon became clear that this technique simply did not scale.

• This mapping between names and IP addresses is extremely important because as humans we prefer to remember names as opposed to long sequences of numbers.

• The exchange of host files between sites was simply to expensive, complex and inefficient. A site had to move its host database to everywhere else.

Site A

Site C

Site B Site D

• The Domain Name System was created to address two problems;

– The organization of the internet.As ARPANET grew researchers began to realize that names for hosts were running out. So they needed to impose a hierarchy/ structure.

– The synchronization of host databases.Again as ARPANET grew it become more and more difficult to keep track of nodes. Data quickly became dated.

So What is DNS For.• In order to understand what DNS is for, you need to

understand the Internet.

• The internet is made up of sites. These sites reflect networks or organisations.

• Organisations can be grouped together depending on type.

• Entities can be grouped together based upon geographic locality.

• DNS provides order to the network, allowing for this grouping of sites.

• It makes the management of the ‘global network’ easier.

• Ultimately DNS provides the following kind of functionality;

– A hierarchal namespace for IP addresses.

– A distributed database of host information.

– A mechanism for finding services and nodes on a network.

– A protocol for exchanging naming information to keep data up to date and synchronised between sites.

The Domain Name System Architecture

• Okay, now that we understand the rationale behind the existence of DNS - how does it work?

• The Domain name system defines a tree of domains. Each domain represents a chunk or grouping of the network which is managed by a single administrative entity.

• The Domain Name Service is a global infrastructure managed by ICANN.

• The Domain Name System defines what are known as Top Level Domains (TLD’s).

• These TLD’s have not been changed in years. They reflect specific kinds of networks.

• As the Internet has grown however ICANN has added a few top level domains.

• Top level domains are sometimes referred to in the literature are gTLD’s (generic top level domains).

• Most of the top level domains are used within the United States. Outside the United states there are a number of top level country code domains ccTLD’s.

Domain Use Domain Use

com Commercial Entities net Network Providers

edu Education Entities org Non profit organisations

gov Government int International

mil Military Networks arpa Old Style Arpanet

• Some common country codes are;

• Most of these countries produce second level domains which are similar to the top level domains offered by the US.

Code County Code Country Code Country

au Australia fi Finaland hk Hong Kong

ca Canada fr France ch Switzerland

br Brazil jp Japan mx Mexico

de Germany se Sweden mu Hungary

• For example the internet has the following structure.

• So considering this, www.uow.edu.au belongs to the uow domain which is part of the edu domain which is in au’s namespace.

.au

.com .edu .org

Top LevelDomain

SecondLevel

Domain

other gTLD’s wouldappear at this level.

• DNS allows us to efficiently resolve names to numbers.

• Using this system, we can identify a single node, in a network in a particular country.

Who manages the DNS namespace

• The DNS namespace provides identification for networks and nodes. Without it the Internet would not exist in its current form.

• Domains such as uow are sub domains, we are guaranteed they are unique. This guarantee is made through the way the system is managed.

• The management of the top level domains was formerly coordinated by Network Solutions Inc, under contract from the National Science Foundation.

• It was one great big monopoly.

• Now any organisation can opt to have a top level domain, we are beginning to see them in the form of .mov, .sex etc.

• Domains largely emerge due to congestion in the namespace –

• Regional top level domains are managed by local authorities. For example in Australia is it auNic. The control is authorised by ICANN.

• The management of educational domains in Australia is done by a private sector organisation. (Educause http://www.educause.edu/edudomain/)

• If an organisation wishes to have a .com.au or .edu.au domain they need to speak to the appropriate authority.

• Each domain on the Internet has at least one DNS server which keeps track of the network.

• These DNS servers talk to there parent server and serve requests of clients around the world.

• The top level domains have what are known as ‘root’ name servers. These process a huge number of requests and updates.

• DNS is the way that Internet names are resolved to IP addresses, e.g.uow.edu.au to 130.130.37.201

• DNS lookup cascades, if the local DNS does know the IP then it asks other DNS servers

• There are 13 root DNS• try the ‘nslookup’

command

Obtaining a Domain.• Depending upon where you wish to create a

domain you need to work with different agencies.

• ICANN is responsible for delegating ‘authority’ to agencies to handle certain top level domains.

• In Asia Pacific ww.apnic.net has a registry of all the domain and organisations that are managed.

Problems with the Domain Name Service

• Some organisations see DNS as a problem. This has been a great problem in the past with the ‘monopoly’ management of the infrastructure and service.

• Domain squatting has grown in popularity. Domain squatting is where people by names in particular domains which may be used in the future.

• One day someone will need the name and pay top dollar for it. For example business.com was sold for $3.5 million.(this is just an address of the net - well a domain).

Now its your turn…• Zakon, R. H. (2005) ‘Hobbes

Internet Timeline v8.0’, Zakon Group LLC, Available from: http://www.zakon.org/robert/internet/timeline/

•Using Hobbes Internet Timeline prepare your own timeline of key events (approx. 10) which were important to the development of the Internet and the World Wide Web. •Select three events which you consider to be the most important.•Elect a group member to present this selection to the class•Has the Internet revolution been different to other technological revolutions such as the telegraph